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IBAN Validator

Check whether an IBAN passes its mod-97 checksum — and see the country — right in your browser. It catches typos, not whether the account exists.

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Quick Answer

Enter an IBAN and the tool runs the mod-97 checksum defined by the IBAN standard, telling you whether it passes and showing the country from the first two letters. A pass means the IBAN is structurally valid and its check digits match — which catches almost all typing mistakes. It does not confirm the account exists, is open, or belongs to anyone. It runs entirely in your browser, so the number is never sent anywhere.

What the IBAN Validator Does

This tool validates an International Bank Account Number by recomputing its check digits with the mod-97 method that the IBAN standard uses. Spaces are ignored and letters are read in upper case, so you can paste an IBAN in its usual grouped form.

It is the quick way to catch a mistyped IBAN before you rely on it for a transfer — the same integrity check that banking systems run as a first step, confirming the number is internally consistent.

How It Works

The check rearranges the IBAN by moving the first four characters — the country code and two check digits — to the end. Each letter is then replaced by a number (A is 10, B is 11, up to Z which is 35), producing one very long integer. That integer is divided by 97, and the IBAN is valid only if the remainder is exactly 1.

This single calculation verifies the two check digits against the rest of the number, which is why it reliably catches a wrong or swapped digit. The country is simply read from the first two letters, which follow the standard country codes.

What it checks & how

  1. Normalise the IBAN. Remove spaces, upper-case the letters, and check it is 5 to 34 alphanumeric characters.
  2. Rearrange. Move the first four characters (country code and check digits) to the end.
  3. Convert letters to numbers. Replace each letter with a number (A is 10 through Z is 35) to form one big integer.
  4. Test mod 97. Divide by 97; the IBAN is valid if the remainder is exactly 1, and read the country from the first two letters.

IBAN mod-97 check

move the first 4 characters to the end replace each letter with a number (A=10, B=11, … Z=35) valid if the whole number mod 97 = 1
Worked example
GB82 WEST 1234 5698 7654 32 → passes mod-97 · Country GB · one digit off → fails

The mod-97 test checks the two check digits against the rest of the IBAN, catching around 99% of transcription errors — but a valid checksum does not mean the account exists.

Privacy

Your IBAN never leaves your device. The check runs entirely in your browser with no network request, so nothing is uploaded.

Because the work is local, you can verify a real account number without it being stored or sent anywhere.

Nothing persists between sessions — close the tab and the IBAN is gone.

Standards & references

  • IBAN (ISO 13616) — The international standard for bank account numbers: a country code, two check digits, and a country-specific basic account number (BBAN), up to 34 characters in total.
  • Mod-97 check digits (ISO 7064) — The IBAN's two check digits are computed and verified with the mod-97-10 method. A valid IBAN gives a remainder of 1 when the rearranged, letter-converted number is divided by 97.
  • What it detects — The mod-97 check catches up to around 99% of transcription errors — single wrong digits, swapped digits and similar slips — which is why it is the first line of defence against a mistyped IBAN.

Accuracy & Limitations

The mod-97 calculation is exact and standard, so an IBAN that passes here passes any compliant validator, and the check reliably catches the typing errors it is designed for.

A passing IBAN is structurally valid but not proven real. The checksum confirms the number is internally consistent; it cannot tell you the account exists, is open, accepts transfers, or belongs to the name you expect.

It validates the checksum and the overall length range, but it does not enforce each country's exact IBAN length or BBAN format. A number of the wrong national length could still satisfy the general mod-97 test.

It reads the country from the first two letters without checking that the rest matches that country's specific structure. For a full validation against a country's format, a registry-based validator goes further than the checksum alone.

Real-World Use Cases

Catching a typo

Confirm an IBAN was entered without a wrong or swapped digit before a transfer.

Form validation

Run a client-side IBAN check on a payment or payee form.

Identifying the country

Read the country code from the start of the IBAN.

Learning the algorithm

See how the mod-97 check responds to a single changed digit.

When to use it — and when not to

Good for

  • Catching a mistyped IBAN
  • Client-side payment form validation
  • Reading the country from the IBAN
  • Learning how the mod-97 check works

Not the best choice for

  • Confirming the account exists or is open
  • Verifying the account holder's name
  • Enforcing a country's exact IBAN format
  • Any guarantee a transfer will arrive

To be sure an account is real and reachable, your bank or payment provider verifies it during the transfer — the mod-97 check is only the offline first filter. For full per-country format checks, use a registry-based IBAN validator.

Frequently Asked Questions

What does a passing IBAN mean?
It means the IBAN is structurally valid: its two check digits match the rest of the number under the mod-97 test. That catches almost all typing mistakes, but it does not prove the account exists or is open.
Does this confirm the bank account is real?
No. The mod-97 check only verifies the number's internal consistency. Whether the account actually exists, accepts transfers, or belongs to a particular person can only be confirmed by the bank during a transaction.
How does the mod-97 check work?
The first four characters move to the end, each letter becomes a number (A is 10 up to Z is 35), and the resulting large integer is divided by 97. The IBAN is valid if the remainder is exactly 1.
What errors does it catch?
Around 99% of transcription errors — single wrong digits, transposed digits and similar slips. It is highly effective at flagging a mistyped IBAN, which is its main purpose.
Where do the check digits sit in an IBAN?
They are the third and fourth characters, right after the two-letter country code. The mod-97 calculation verifies them against the rest of the number.
Does it check the country-specific format?
Not fully. It validates the mod-97 checksum and the general length range, but it does not enforce each country's exact IBAN length or account-number structure. A registry-based validator does that extra step.
What do the first two letters mean?
They are the ISO country code identifying where the account is held — GB for the United Kingdom, DE for Germany, and so on. The tool reads the country from them.
Do spaces matter when I enter an IBAN?
No. The tool removes spaces and reads letters in upper case, so you can paste an IBAN in its usual four-character groups or as one block.
Why might a real IBAN fail here?
Usually a typo — a missing, extra or swapped character. Occasionally a number copied with hidden characters can fail. Re-enter it carefully; if it still fails, check the source, as the checksum is rarely wrong for a correct IBAN.
Is my IBAN uploaded anywhere?
No. The check is computed entirely in your browser. Nothing is sent to a server, so the account number stays on your device.
How long can an IBAN be?
Up to 34 characters, depending on the country. The country code and check digits are always the first four; the rest is the country-specific basic account number.
Can it tell me the bank or branch?
Not directly. Part of the IBAN encodes the bank and branch in each country's format, but this tool validates the checksum and shows the country rather than decoding the bank details.

References

Runs the ISO 7064 mod-97 check used by every IBAN; honest that a passing IBAN is structurally valid but not proof the account is real, open or correct.

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